The biological treatment of waste water involves the use of rotating contactor media which provides surfaces for the deposit of waste or biological slimes thereon. The media is positioned in a water treatment tank so that approximately its lower half is immersed in a body of waste water, while its upper half is exposed to the atmosphere. As the media rotates, its halves are alternatively exposed to the waste water and to oxygen in the atmosphere causing the deposit of slime on its surface. Prior art patents recognize the importance of media designs which employ a plurality of discs to enhance surface area. Such designs have adjacent discs interconnected by gluing or welding.